The Behavior of a Poly(aniline) Solid Contact pH Selective Electrode Based on N,N,N′,N′-Tetrabenzylethanediamine Ionophore

Abstract

A hydrogen ion-selective solid-contact electrode based on N,N,N′,N′-tetrabenzylethanediamine has shown the best Nernstian slope and selectivity and the widest response range in a Tris buffered pH sample solution. Its linear dynamic range was pH 3.50–11.94, and the Nernstian slope showed 52.1 mV/pH (at 20 ± 0.2˚C). When it was directly applied to human whole blood (in pH range 6.0–8.5) we could obtain the same satisfying results. This electrode continuously contacted a Tris 7.47 buffered solution, human whole blood and a hydrofluoric acid solution for one month without any loss of performance. Also, hydrofluoric acid did not influence the surface of this electrode, and thus it was maintained without showing any changes in potentials after being used in a hydrofluoric acid solution. The standard deviation in the determined e.m.f. differences was 1.5 mV (N = 5) for Tris buffer solutions of pH 6.5 and 1.1 mV at a Tris buffer solutions of pH 8.5. The 90% response time of the electrodes obtained by injecting of hydrochloric acid into the Tris buffer sample solution was less than 10 s. Especially, in the this paper, with these potential response characteristics of hydrogen ion selective poly(aniline) solid contact electrode, we have also presented the pH response mechanism of this electrode and the role of poly(aniline) and a doped anion in a poly(aniline) layer.